Whisk eggs and sugar in medium metal bowl. Set bowl over pan of
simmering water (do not allow bowl to touch water) and whisk until
mixture is thick and foamy and thermometer registers 160°, about 1
min. Remove bowl and whisk mixture until cool, about 4 min. Whisk
mascarpone in large bowl to loosen. Add egg mixture and vanilla to
mascarpone; whisk to blend.

Invert cake onto waxed paper lined work surface. Cut six 2 1/2-inch
rounds and six 3-inch rounds from cake using cookie cutters. Place
one 2 1/2- inch round in each of six 3/4-cup ramekins. Brush cake in
each ramekin with 1 Tbsp coffee syrup.

Top each cake with generous 1/3 cup mascarpone cream. Top each with
a 3-inch cake round and brush with 1 Tbsp coffee syrup. Cover with
plastic and refrigerate until cold, at least 3 hours or overnight.
Top each dessert with grated bittersweet chocolate and a dollop of
whipped cream.